Tire cords and fabrics and tires including the same



United States Patent C) TIRE CORDS AND FABRICS AND TIRES INCLUDING THE. SAME Folsom E. Drummond, Washington, D. C., and Leo J. Novak, Dayton, Ohio, assignors to The Commonwealth Engineering Company of ()hio, Dayton, Ohio, a corporation of Ohio No Drawing. Application June 24, 1953 Serial No. 363,942

3 Claims. (Cl. 152-359) This invention relates to an improved cord or fabric, and more particularly to a novel tire cord or fabric.

Various problems arise in connection with cords or fabrics used to reinforce pneumatic tires. All such cords or fabrics are subjected to more or less severe flexing during service and, for satisfactory performance, must have a long flex-life at elevated temperatures, should not flow under stresses, and should adhere tenaciously to rubber. All of the available tire cords can be improved in one or more of these respects. Thus, it is known that cotton cords have a low flex life. Native cotton cellulose is known to consist of long, unbranched, primary valence chains of anhydro-B-glucose units. In sub-microscopic structure this native cellulose is disposed in two com ponents, one dense, crystalline and discontinuous, the other non-crystalline, amorphous or expanded, this latter component supplying the continuity of structure between the small crystalline blocks. It appears that the two components are not sharply distinguishable, but that there is a gradual transition from truly dense crystalline blocks of cellulose to the most expanded, amorphous part of the surrounding network'so that the structure comprises intervening semi-crystalline regions. The blocks of crystalline cellulose, or crystallites, are apparently rigid, whereas the amorphous cellulose is labile, and these differences are believed to account for the properties of cotton tire cords, i. e., high strength due to the long primary valence chains and comparatively low flexibility due to the labile, easily-deformed amorphous regions. The amount of Wholly amorphous cellulose in native cotton being low, the flexibility and deformability or plasticity are also low. The semi-crystalline (or semi-amorphous) regions are therefore important. The presence of sufiicient water in the cotton fibers to cause swelling thereof has the eifect of producing expansion of those regions of intermediate density and, in effect, of increasing the amount of labile, expanded network. However, high tire temperatures dehydrate the fibers and, apparently, as the water is driven out the fiber structure collapses, with increase in the length of the rigid, crystallites and decrease in the labile, non-crystalline cellulose, as a consequence of which the fibers lose flexibility, becoming stiff and rigid. When this happens and the cotton tire .cord is flexed, the dry, stiff fibers comprising it do not cling together but slip over one another very readily. The abrasion of the dry fibers resulting from this slippage induces early failure of the cord. Also, when the cord comprising the dry, structurally collapsed fibers is subjected to a load, the fibers resist the deforming force, and this resistance naturally contributes to premature failure of the cord in service.

Cords made of artificial and synthetic fiber-forming materials, while showing improvement in some respects as compared to raw cotton cords, also exhibit disadvantages and their successful use as tire reinforcements presents problems. For instance, it is known that cords made of regenerated cellulose tend to flow under the prolonged high stresses to which they are subjected when used in tires. Furthermore, along with cords made of nylon and other fiber-forming synthetics, the regenerated cellulose cords, being formed of filaments having smooth, slick surfaces, do not adhere to rubber.

One object of this invention is to provide tire cords and fabrics having improved flex life at high temperatures regardless of the type of fibers or filaments from which the cords are formed.

Another object is to provide reinforcing cotton cords and fabrics for pneumatic tires which have, in effect, increased density and in which slippage of the individual fibers relatively of each other is inhibited or prevented.

A further object is to provide regenerated cellulose tire cords having high flex life at elevated temperatures, which do not tend to flow under prolonged high stresses, and which adhere strongly to rubber.

An additional object is to provide tire cords of nylon and other fiber-forming synthetics having high flex life at elevated temperatures and which adhere strongly to rubber.

These and other objects of this invention are accomplished by treating all types of tire cords, or tire-reinforcing fabrics comprising them, with an aqueous or nonaqueous solution or dispersion of a dextran.

The dextrans are high molecular weight, branched polysaccharides comprising anhydroglucopyranosidic units joined by molecular structural repeating alpha-1,6 and non-alpha-1,6 linkages, at least 50% of these linkages being, apparently, of the alpha-1,6 type.

A wide variety of dextrans which differ with respect to their specific physical properties, such as molecular weight, the molecular structural repeating alpha-1,6 to non-alpha-l,6 linkages ratios, the extent of branching (length and distribution of side chains or groups) and the osmotic pressure in liquids are available.

In practicing the present invention, there is used a solution or dispersion of a dextran having a molecular structural repeating alpha-1,6 to non-alpha-1,6 linkages ratios in the range between 1.921 and 30:1, a molecular weight of from about 5,000 to x10 as determined by lightscattering measurements, a solubility or dispersibility in water such as to yield colloidally stable aqueous solutions or dispersions of from 0.5% to 50% by weight concentration, and a colloidal osmotic pressure in liquids of from 1 mm. Hg to 300 mm. Hg. In certain embodiments, the aqueous solution or dispersion may contain organic solvents or diluents, as will be explained more in detail hereinafter, or the liquid vehicle may be an organic solvent in which the dextran is dissolved or dispersed but which is inert with respect to the material of which the cord is formed and also inert to rubber.

The dextran used may be obtained by any of the available methods, including bacterial conversion of 1.4 linkages of dextrins to 1,6 linkages of dextran. Usually, it is obtained by inoculating a sucrose-bearing nutrient medium With a dextran-producing microorganism such as those of the Lezrconostoc mesenteroides or L. dextranicu'm types, or the enzyme of the microorganisms, and holding the mass until the dextran is synthsized from the sucrose in maximum yield, after which the dextran is precipitated by the addition of a non-solvent such as a Water-miscible alcohol or ketone, e. g., methanol, ethanol, isopropanol or acetone. Under normal conditions, the native dextran thus obtained has a molecular weight calculated to be in the millions. It may be reduced to particulate-condition for solution or dispersion in a solvent to provide media for application to the tire cords or fabrics.

Instead of using native dextran, whether relatively crude or substantially pure, there may be used dextrans having lower molecular weights. The lower molecular :centration by weight.

weight'd'extr'ans, i. e;', thosehaving weights as low as 5000 or even lower; may be produced directly or'they may be obtained by hydrolysis of native dextrans, the hydrolysis being effected in any suitable way, as by meansof acid orenzymatically; and if desired the' by drolysis product may be fractionated toobtain a'fraction' ofuniform'or more nearly'uniform' molecular weight.-

The-dextran usedmay be aninitiallywater-soluble dextran obtained bythe use of microorganisms bearing the following NRRL classifications: Leuconostoc m'esenteroides B-512, B-l 19, 13-1146, B-1l90 or a water-insoluble or substantially Water-insoluble but water-dispersible dextran obtained by the use of Leuconostoc mesenteroides- -B742,' 13-1191, 13-1196, B-l208, B-l21'6, B-ll,--B-l144,-B523, Streptabacterium dextrz'micu'm 13-1254 and i =Betabacterium vermiforme I B-l 139.

Thedextran is applied to the tire-cords in theform of a stable aqueous solution or dispersion whichm'ay havea dextran concentration of from 0.5 to=50% con In general, solutions or' dispersions containing from-5% to by weight of the dextran are satisfactory. These solutions or dispersions, may also comprise an organic solvent in any amount between 0.5% and 35% by weight.

Treatment of the cords with the dextran solutionior' capillaries, the water ofthe treating medium servingtoswell-the-cotton fibers as it carries the dextraninto the fiber structure, and thenldrying the treated cord-to'obta-in aicord'comprising small particles or minute masses ofthe amorphous dextran deposited in-the swollen network of intramicellar capillaries, which amorphousdeposits have the effect of counteracting the tendency of the fiber structure to collapse at high temperatures and of increasing the proportion of the fiber which is amorphous, expanded-and labile, thus increasing the capacity of the cord to Withstand the deformationincidental: to flexing of the cord in service. The dextran, .being amorphous, isparticularly suitable for this purpose of seem. ingly augmenting the amorphousregions of the cotton fibers. The :presence of the dextran in the fiberstends to prevent collapse of the fiber which normally attends dehydration of the cord at high temperatures.

Inn'oductionof. the vdextran into the cotton fibers may beaccomplished by treating the cord with the dextran solution or dispersion at elevated temperatures, for example by heating the raw cotton cord in a concentrated dextran solutionor: dispersion, the heating serving .to facilitate the displacement of' air occluded in the capillaries and aiding penetration of the fiber by the dextran.- Or the impregnation may be facilitated by'supportinga squeezing device, such as a pair of rollers, in submerged condition in the solution or dispersion and passing the cord between them so that the pressure'of the rolls on the cord will expedite expulsion of the air. andlaid' uniform distribution of the dextran'through'the fibers and cord, including such areas thereof as contain previously absorbed moisture. method of accomplishing the impregnation involves evacuating air from the cord and then passing it through the solution or dispersion under pressure.

Another alternative The dextran may also be applied to the raw tireicord' immersing or dipping the cordin the medium or'bycon tinuouslydrawing the cord through the medium;

' The presence of the dextran in-the' fibers'or in 'oron the cord tends to inhibit slippage of the individual fibers relatively of-each other and to bind the fiberstOgetherinto a unitary strong structure.

In applying the dextran solution or suspension to tire cords formed of fibers or filaments characterized by a sleek surface, the foregoing conditions may be employed, to. obtain, after drying, a structure-in which the individual filaments or yarns are boundtogether by the dextran which inhibits wearing and abrasion of the filaments or fibers-against each other, in'the case of reg en erated cellulose cords more particularly, tends" to stabili'ze the structureand counteract flowing of the material under prolonged high stresses, and generally improves the properties of the cords includingtheir ability to accept deformation of flexure.-

The dextrans do not have definite melting points and are not melted at the high tire temperatures. They may develope an inherent latent adhesiveness under heating but this'may'be regarded as advantageous in'that it assists in anchoringtherubber to the cords. the cordsare formed of-fibers or filaments having slick,

smoothsurfaces and which normally require treatment with an adhesive to insure anchoring of the rubberto" the cords, it is-generally preferred to treat the cords with a dextran medium comprising, in addition to the dextranand water, an organic solvent. iently,- there maybe-used the three-component composition obtainedIby-precipitating a microbiologically' produceddextran from an aqueous fermentate by the use" The three-- component composition, after drying on the cords, is stronglyadhesiveand adheres to both the cord and to rubber,v while impregnating or coating the cordi withdextran- Thatcomposition thus servesthe dual-purpose"- of:anchoring the rubber firmly to the cord and of'irnof; a loweraliphatic.- alcohol or acetone.

proving the flex-life and other properties of the cord..

The treated cords, after removal of the excess'treating medium and drying thereof, are formed into afabric" of the: cord type which is substantially weftless but. may, and usually does, comprise a pick thread to keep the cords in' place, and the fabric is passed through a calender in whichrubber is applied to it.

Instead-of applying the dextran to the cords and then fabricating them, the dextran may be applied-to the WCfG less-fabric, the excess treating medium may be removed, as by blowing, after which the fabric may be dried and passed through acalender in which rubber is applied to it; The fabric may be constructed in any suitable way;

treated with the dextran solution or dispersion, including the time and temperature, are controlled to insure the desired 'dextran pickup, which may be from 5% to 50% or. even higher by. weight.

The following examples are illustrative of specific embodiments of the invention.

Example 1 Rayon tire cords are-formed intoa tire fabric and the fabric is dipped into a treating composition comprising. about 70-66% of water, about 10% by weight of'a high molecular weight native B5 12 dextran and 'about20- 24% by weight of isopropyl alcohol, atroom temperature, removed from the medium, subjected to a'stream of air toblow outexcess treating'rnedium anddriedi The dried fabric comprises about 20% byweight of the dextranand hasatacky surface. It is wound ap on -a- However, when Very conven-' roll, from which it is supplied to a calender of the usual type and in which the rubber deposit is sheeted out onto the fabric and forced onto and between the cords of the fabric. After leaving the calender, the fabric having the rubber adhered thereto, may be taken to other equipment such as the bias cutter, etc.

The native B-512 dextran used in this example is the high molecular weight dextran obtained by inoculating an aqueous sucrose-bearing nutrient medium with Leuconostoc mesenteroides 13-512 whole culture or the enzyme filtered from the culture, incubating the mass, precipitating the dextran formed from the fermentate and drying the precipitate.

Example 11 Conventional cotton tire cords are passed through a hot 50% aqueous solution of dextran of relatively low average molecular weight (5,000 to 30,000) at a speed to insure contact time of three minutes between the cords and hot solution. The impregnated cords are then stretched between rollers while blowing air against them to remove excess treating medium, and dried. The dried impregnated cords are formed into the usual weftless fabric, which is passed through a calender in which the rubber is sheeted out on the fabric and pressed on and into it.

Example 111 A nylon tire fabric is treated as in Example I to obtain a fabric of good flex-life and to which the rubber is firmly anchored.

Instead of applying the dextran to the cords in an aqueous medium, non-aqueous solutions or dispersions thereof in inert organic solvents may be used, such as solutions or dispersions in acylamides, such as formamide or the dialkylated acylamides of the type of dimethylformamide.

Cords (or the fabrics comprising them) formed of other types of slick-surfaced filaments or fibers may be treated in accordance with this invention, such as those of polyesters like polymethylene terephthalate and poly- 6 amides or polycarboanhydrides of the type derived from alpha-amino acids to obtain stabilized cords and fabrics of good flex life for incorporation in pneumatic tires.

It will be understood that, while there have been described certain specific embodiments of this invention, it is not intended to thereby limit or circumscribe it by the details given, in view of the fact that this invention is susceptible of various modifications and changes which come within the scope of this disclosure and of the appended claims.

We claim:

1. In the manufacture of rubberized tire reinforcement cords the improvement which consists in providing cords of synthetic filaments, treating the resultant cords with an aqueous solution of dextran, removing the excess of dextrain solution from the cords, thereafter drying the dextran treated cords, and dipping the thus treated cords in rubber to provide rubberized dextran-coated tire cords.

2. In the manufacture of rubberized reinforcement cords the improvement which consists in providing cords of synthetic filaments, treating the resultant .cords with an aqueous solution of dextran, said aqueous dextran solution comprising by weight of dextran, removing the excess of dextran solution from the cords, thereafter drying the dextran treated cords, and dipping the thus treated cords in rubber to provide rubberized dextrancoated tire cords.

3. A pneumatic tire which comprises rubber and reinforcing cords, said cords consisting of regenerated cellulose impregnated with dextran and having an outer coating of rubber.

References Cited in the file of this patent UNITED STATES PATENTS 2,503,624 Luaces Apr. 11, 1950 2,645,266 Muller et al. July 14, 1953 2,665,733 Buckwalter Ian. 12, 1954 2,706,690 Deniston Apr. 19, 1955 

3. A PNEUMATIC TIRE WHICH COMPRISES RUBBER AND REINFORCING CORDS, SAID CORDS CONSISTING OF REGENERATED CELLULOSE IMPREGNATED WITH DEXTRAN AND HAVING AN OUTER COATING OF RUBBER. 